Remote control (RC) ground vehicles are typically controlled with a transmit controller which has two components: a steering knob, also called a steering wheel, and a throttle/brake control. A human driver familiar with this control interface is able to adeptly drive a ground vehicle regardless of the vehicle's orientation with respect to the driver. Thus, the driver may be capable of driving the vehicle whether it is facing toward the driver or away from the driver. The driver may also easily execute high speed turns with a RC ground vehicle.
The same driver, however, may encounter difficulty when piloting an RC air vehicle. Piloting a conventional RC air vehicle requires significantly more skill than driving a RC ground vehicle. The conventional two-stick aircraft controller requires a pilot to control the aircraft's throttle and yaw and pitch and roll independently. The pilot must be aware of the orientation of the aircraft when applying the controls, which requires significantly more awareness than being aware of the orientation of a ground vehicle. Making a “coordinated turn” with an RC aircraft requires the pilot to simultaneously input yaw, pitch, and roll commands in order to command the aircraft to turn in the air without “skidding” (sliding to the outside) or “slipping” (dropping towards the inside) in the turn. At the same time the pilot must also make adjustments to the throttle command to control or maintain the aircraft's altitude.
It would be desirable if a pilot of an RC air vehicle could take greater advantage of the pilot's familiarity with the controls of an RC ground vehicle.
Conventional RC aircraft are controlled with a “two stick” transmit controller as previously described. A typical Mode 2 transmitter will be configured as shown in FIG. 14. Moving the left stick fore and aft controls throttle; moving it left and right controls yaw. Moving the right stick fore and aft controls pitch; moving it left and right controls roll. In the example of a fixed-wing aircraft, moving the left stick fore and aft will increase or decrease the thrust from the power source (electric motor or combustion engine). Move the left stick left and right will move the rudder control surface to yaw the airplane to the left or right. Moving the right stick fore and aft will move the elevator control surface(s) to pitch the airplane up and down. Moving the right stick left and right will move the aileron control surfaces to roll the airplane to the left or right.
Conventional two-stick transmitters may be configured with a “mix” between one or more controls. For example, a transmitter could be configured so the rudder moves when the ailerons are commanded to move. In this example, when moving only the right stick left and right, a percentage of rudder movement can be commanded. This may result in a so-called coordinated turn in which the airplane will both bank and yaw at the same time. Coordinated turns in fixed-wing aircraft may be useful to counteract the effects of adverse yaw, for example. In the example of a multi-rotor aircraft such as a quadcopter, coordinating bank angle and yaw together may be extremely useful in executing natural looking turns without “skidding” or “slipping”.
One conventional two-stick transmitter that can be configured with a “mix” is the Futaba 8J. Both linear and non-linear (5 point) mixes can be configured. Pages 65-69 of the product manual contain detailed description of the mixes available. The entirety of the Futaba 8J product manual is hereby incorporated by reference. The four linear programmable mixes available on the Futaba 8J are setup by default as: 1) aileron to rudder for coordinated turns, 2) elevator to flap for tighter loops, 3) flap to elevator to compensate pitching with flaps and 4) throttle to rudder for ground handling compensation.
Pre-configured mixes may be available on some ready-to-fly (RTF) aircraft which use simple transmitters that are not programmable by the end user. One example is the Hobbyzone Firebird Stratos, by Horizon Hobby. Using its Virtual Instructor Technology, as shown in FIG. 15, this aircraft uses at least three different mixes: 1) rudder to elevator mixing, 2) throttle to elevator mixing and 3) rudder to motor mixing. See page 6 of the Firebird Stratos Instruction Manual for more details. The entirety of the Firebird Stratos Instruction Manual is hereby incorporated by reference.
Non-conventional “single stick” transmitters were popular for some time in 1970's and the 1980's. These transmitters relocated control of the rudder to the right stick, by using a knob at the tip of the stick, as seen in FIG. 16. Rotating the knob to the right (clockwise) would result in the same control as pushing the conventional rudder stick of FIG. 14 to the right. Rotating the knob to the left (counter-clockwise) would result in the same control as pushing the conventional rudder stick of FIG. 14 to the left. The throttle was controlled by a slider, typically actuated by the pilot's left thumb. The Futaba FP-T8SSA-P transmitter is one example of a “single stick” transmitter. Mixing was available on this Futaba single-stick radio, the details of which can be found at least on pages 5, 29, 30, 32, 33 and 34 of the Futaba FP-T8SSA-P Instruction Manual. A quote from page 33, titled AILERON→RUDDER MIXING, “This function is sometimes referred to as ‘CAR’ (Coupled Ailerons and Rudder) and is useful on sailplanes and certain scale models where aileron and rudder must be used together for coordinated turns.” The entirety of the Futaba FP-T8SSA-P Instruction Manual is hereby incorporated by reference.
The entirety of each of the following U.S. Patents is hereby incorporated by reference: U.S. Pat. No. 8,473,117 to McConville; U.S. Pat. No. 6,227,482 to Yamamoto; and U.S. Pat. No. 8,200,375 to Stuckman et al. The subject matter disclosed in each of the aforementioned patents may be utilized or adapted to control single-rotor, multiple-rotor and/or fixed-wing aircraft as discussed herein.
Aftermarket aircraft control systems are available that utilize more advanced electronics and control systems to improve control of the aircraft and sometimes to automate certain functions. One example is the Guardian by Eagle Tree Systems. The Guardian is specifically made for fixed-wing aircraft and uses both accelerometers and gyroscopes. In its 2D Mode it provides wing leveling stabilization, returning the model to level flight when needed. In 3D mode it works to smooth out turbulence and stall characteristics. The Guardian also includes Automatic Turn Coordination which employs the “step on the ball” method to actuate the rudder in order to coordinate turns. As the aircraft enters a banked turn the Guardian will actuate the rudder and “step on the ball” to perform automatic turn coordination. There are many other features available on the Guardian as shown in the product literature and Guardian Instruction Manual. The Guardian 2D/3D Stabilizer Manual and the Instruction Manual for Guardian Stabilization Expander by Eagle Tree Systems are hereby incorporated by reference.
APM, a popular open-source autopilot suite, released version 3.1 of their APM:Copter in December of 2013. In this version they included a new flight mode called “Drift Mode”, which allows the pilot to fly a multirotor helicopter as if it were a plane with built in automatic coordinated turns. The pilot has direct control of yaw and pitch, but roll is controlled by the autopilot. The right stick controls pitch and yaw and the left stick is for manual altitude control via the throttle. When the aircraft is moving forward and the pilot pushes the right stick to the left or right to make a turn, the aircraft will also bank at the same time, to make a coordinated turn in that direction. Drift mode relies on GPS to function. Yaw and roll are mixed based on velocity. More information can be obtained by visiting the APM website, http://copter.ardupilot.com/. The APM:Copter documentation available in the ArduCopter Multirotor UAV web pages at http://copter.ardupilot.com/, including but not limited to the “Manual for 8 Channel PPM Encoder (v2), Firmware: v2.3.16” and “PPM Encoder” instruction manual by 3DRobotics, are hereby incorporated by reference.